1. Field of the Invention
This invention relates to a circuit in a coffeemaker for detecting the presence of calcium deposits. More specifically, the circuit detects an excessive calcium buildup and signals to indicate this buildup.
2. Discussion of the Prior Art
In the past, numerous attempts have been made to detect mineral deposit buildup in automatic coffeemakers. This buildup is caused by a calcium carbonate depositing in the hot water outlet tube of the coffeemaker when the water is heated to sufficient temperatures. The buildup has to be removed periodically and the user must be signalled that such removal is necessary. Past attempts have included indicators to alert the user of this buildup.
U.S. Pat. No. 4,827,837 to Johnson et al. discloses a calcification indicator which operates to notify the user to clean the accumulated mineral deposits. The device utilized to sense the mineral deposit is either electromechanical or a logic circuit.
U.S. Pat. No. 4,141,286 to Smit describes an apparatus for enabling the user to see scale deposits in the outlet pipe. The outlet pipe of the coffee making apparatus is made of transparent material to allow visible inspection by the user.
U.S. Pat. No. 4,139,761 to Obrowski discloses a calcification indicating device in a household coffee machine. The device is connected in parallel with a heating thermostat. At a predetermined temperature, the thermostat opens and the calcification indicator turns on to indicate cleaning of the coffee maker is necessary.
U.S. Pat. No. 4,214,148 to Fleischhauer describes a water heater in a coffee maker having means for indicating calcification of the water heater. A switching circuit utilizes a temperature range to indicate calcification.
U.S. Pat. No. 4,292,499 to Kleinschmidt et al. discloses a system using PTC resistors positioned at a water entry and exit. A circuit determines a differences in current flow which is associated with calcification. An indication is made when cleaning is necessary.
The calcification systems exemplified in the patents referred to hereinabove illustrate the many improvements made over the years in simplifying and improving this aspect of electric coffeemakers. There still exists, however, in this industry, a need for a calcification circuit which detects mineral deposits in a manner that particularly improves the safety, efficiency and economy of the electric drip coffeemakers, and simplifies installation, operation and accountability.